gen.subproj/getifaddrs.3

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   3 .\"     BSDI    getifaddrs.3,v 2.5 2000/02/23 14:51:59 dab Exp
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  25 .Dd October 12, 1995
  26 .Dt GETIFADDRS 3
  27 .Os
  28 .Sh NAME
  29 .Nm getifaddrs
  30 .Nd get interface addresses
  31 .Sh SYNOPSIS
  32 .Fd #include <sys/types.h>
  33 .Fd #include <sys/socket.h>
  34 .Fd #include <ifaddrs.h>
  35 .Ft int
  36 .Fn getifaddrs "struct ifaddrs **ifap"
  37 .Ft void
  38 .Fn freeifaddrs "struct ifaddrs *ifp"
  39 .Sh DESCRIPTION
  40 The
  41 .Fn getifaddrs
  42 function stores a reference to a linked list of the network interfaces
  43 on the local machine in the memory referenced by
  44 .Fa ifap .
  45 The list consists of
  46 .Nm ifaddrs
  47 structures, as defined in the include file
  48 .Aq Pa ifaddrs.h .
  49 The
  50 .Nm ifaddrs
  51 structure contains at least the following entries:
  52 .Bd -literal
  53     struct ifaddrs   *ifa_next;         /* Pointer to next struct */
  54     char             *ifa_name;         /* Interface name */
  55     u_int             ifa_flags;        /* Interface flags */
  56     struct sockaddr  *ifa_addr;         /* Interface address */
  57     struct sockaddr  *ifa_netmask;      /* Interface netmask */
  58     struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */
  59     void             *ifa_data;         /* Address specific data */
  60 .Ed
  61 .Pp
  62 The
  63 .Li ifa_next
  64 field contains a pointer to the next structure on the list.
  65 This field is
  66 .Dv NULL
  67 in last structure on the list.
  68 .Pp
  69 The
  70 .Li ifa_name
  71 field contains the interface name.
  72 .Pp
  73 The
  74 .Li ifa_flags
  75 field contains the interface flags, as set by
  76 .Xr ifconfig 8
  77 utility.
  78 .Pp
  79 The
  80 .Li ifa_addr
  81 field references either the address of the interface or the link level
  82 address of the interface, if one exists, otherwise it is NULL.
  83 (The
  84 .Li sa_family
  85 field of the
  86 .Li ifa_addr
  87 field should be consulted to determine the format of the
  88 .Li ifa_addr
  89 address.)
  90 .Pp
  91 The
  92 .Li ifa_netmask
  93 field references the netmask associated with
  94 .Li ifa_addr ,
  95 if one is set, otherwise it is NULL.
  96 .Pp
  97 The
  98 .Li ifa_dstaddr
  99 field references the destination address on a P2P interface,
 100 if one exists, otherwise it contains the broadcast address.
 101 .Pp
 102 Note that as a convenience,
 103 .Li ifa_broadaddr
 104 is defined by a compiler
 105 .Li #define
 106 directive to be the same as
 107 .Li ifa_dstaddr .
 108 .Pp
 109 The
 110 .Li ifa_data
 111 field references address family specific data.  For
 112 .Dv AF_LINK
 113 addresses it contains a pointer to the
 114 .Fa struct if_data
 115 (as defined in include file
 116 .Aq Pa net/if.h )
 117 which contains various interface attributes and statistics.
 118 For all other address families, it contains a pointer to the
 119 .Fa struct ifa_data
 120 (as defined in include file
 121 .Aq Pa net/if.h )
 122 which contains per-address interface statistics.
 123 .Pp
 124 The data returned by
 125 .Fn getifaddrs
 126 is dynamically allocated and should be freed using
 127 .Fn freeifaddrs
 128 when no longer needed.
 129 .Sh RETURN VALUES
 130 .Rv -std getifaddrs
 131 .Sh ERRORS
 132 The
 133 .Fn getifaddrs
 134 may fail and set
 135 .Va errno
 136 for any of the errors specified for the library routines
 137 .Xr ioctl 2 ,
 138 .Xr socket 2 ,
 139 .Xr malloc 3
 140 or
 141 .Xr sysctl 3 .
 142 .Sh BUGS
 143 If both
 144 .Aq Pa net/if.h
 145 and
 146 .Aq Pa ifaddrs.h
 147 are being included,
 148 .Aq Pa net/if.h
 149 .Em must
 150 be included before
 151 .Aq Pa ifaddrs.h .
 152 .Sh SEE ALSO
 153 .Xr ioctl 2 ,
 154 .Xr socket 2 ,
 155 .Xr sysctl 3 ,
 156 .Xr networking 4 ,
 157 .Xr ifconfig 8
 158 .Sh HISTORY
 159 The
 160 .Nm
 161 implementation first appeared in BSDi
 162 .Bsx .